Hydraulic cylinder control for bulldozer



June 2, 1970 D. H. SEABERG 3,515,224

HYDRAULIC CYLINDER CONTROL FOR BULLDOZER Filed 001;. 5. 1967 2Sheets-Sheet 1 m'vz/vm? DA V/D hf 55A BERG ar 4n June 2, 1970 D. H.SEABERG 3,515,224

HYDRAULIC CYLINDER CONTROL FOR BULLDOZER Filed Oct. 5, 1967 2Sheecs$heet 2 //Yl /YTOR DA Wu H. 554 BERG United States Patent3,515,224 HYDRAULIC CYLINDER CONTROL FOR BULLDOZER David H. Seaberg,Burlington, Iowa, assignor to J. I.

Case Company, Racine, Wis., a corporation of Wisconsm Filed Oct. 5,1967, Ser. No. 673,191 Int. Cl. E02f 3/76 US. Cl. 172-809 2 ClaimsABSTRACT OF THE DISCLOSURE A hydraulic control for a vehicle having ablade, a tilt cylinder, lift cylinders for positioning the blade inrelation to the ground, and valves in the lift cylinders for relief offluid pressure and for allowing by-pass of the fluid. The valves in eachlift cylinder are connected by a pin and the relief and by-pass actionis actuated by reason of one or the other extremity of the valvemechanism striking a portion of the cylinder.

BACKGROUND OF THE INVENTION The invention relates to earth workingequipment Wherein a blade is attached to the front of a vehicle and theblade can be moved in relation to the ground. The prior art relevant toa bulldozer of this type is taught in Long 2,942,363 which shows liftcylinders adjacent the tractor body and strut cylinders for varying thepitch and tilt of the blade. The lift cylinders are pivotally connectedto an equalizing bar which is swivelly connected to the blade andenables the blade to be freely moved without strain on the liftcylinders or frame members. A twisting of the blade and frame membersshould be minimized or eliminated and thus prevent stress and strain onthese members. This type of equalizing, however, has limitations due toits mechanical nature, wherein some binding may occur between thecylinder rods and the swivel joint.

Other means of equalizing stresses and strains in dual operation ofhydraulic cylinders have been accomplished with unloading or reliefvalves, which operate when the fluid pressures become suflicientlygreat. The prior art also shows by-pass valves in cylinders which valvesare positioned laterally such that one opens prior to the other whenapproaching the end of the stroke. These valves permit fluid to by-passthe piston in one cylinder and to flow to the other cylinder. Thesestructures also have limitations when applied to a bulldozer bladebecause of insufficient flexibility.

SUMMARY OF THE INVENTION The present invention relates to a tractorcarrying a dozer blade on the front, the blade being positioned by meansof hydraulic lift cylinders and a tilt cylinder. The invention moreparticularly relates to a control means for the lift cylinders wherein apair of poppet valves are contained within each lift cylinder, thevalves being aligned and connected by a pin. The pin is positioned suchthat as the cylinder piston approaches one end of the cylinder, the pinstrikes the cylinder end and unseats one of the valves. As the cylinderpiston approaches the other end, an actuating sleeve and pin assemblystrikes the cylinder gland and the other valve is unseated. When one orthe other of the valves is unseated the pressurized fluid by-passes therod and piston assembly and the fluid is returned to a supply tank. Thelay-pass pressure is just suflicient to hold the load in any positionofthe blade.

. The lift cylinder rods are connected to and move with the blade andthe tilt cylinder is connected to the blade to vary its tilt and pitch.The lift cylinders are free to oscillate when the tilt cylinder isoperated since the lift cylinders are hydraulically connected inparallel. The hydrauic circuiting permits free movement of the liftcylinders, as the blade is tilted or pitched, by reason of the liftcylinders beign directly connected to the blade.

The advantages of the poppet valves in the lift cylinders permit asimpler and less costly frame assembly as this eliminates the use of anequalizer member. It is also important in the operation of the tiltcylinder to have the lift cylinder pressures relieved to the extent thatthe holding pressure is permitted to return to the tank. Twisting of thetractor frames and blade by the cylinder not yet at the end of itsstroke is prevented because the pressure on that cylinder is justsufficient to hold the blade in position.

Other features and advantages will be realized and will become apparentfrom a reading of the following description taken together with theannexed drawings, in which:

FIG. 1 is a perspective view of a vehicle incorporating the invention;

FIG. 2 is a front view on a reduced scale showing the blade in tiltedpositions;

FIG. 3 is an enlarged sectional view of a lift cylinder showing theconnecting pin, and the valves in the open position;

FIG. 4 is a similar view showing fragmentarily the cylinder with one ofthe valves closed, and

FIG. 5 is a circuit diagram, imposed in perspective, of the hydraulicsystem.

As seen in the perspective view in FIG. 1, the invention is applicableto a vehicle shown as a tractor 10 carrying a blade 12 on the front, thecombination being a bulldozer of well-known type. Tractor 10 includes aframe 14 propelled by the engine and carried on endless tracks 16. Blade12 is carried on push arms 18 and 20, also seen in FIG. 5, pivotallymounted from the track suspension system at the rear thereof by pins 22and 24 and also are pivotally connected to the blade .by pins 26 and 28.The blade and push arms are arranged and constructed to be raised andlowered in relation to the ground around pins 22 and 24.

Hydraulic lift cylinders 30 and 32 are pivotally connected to thetractor by means of trunnions 34 and 36 which can rotate on the sides ofthe tractor to permit the tilting and raising and lowering of the blade12, as described and shown, so the cylinders 30 and 32 are connecteduniversally at the tractor, as shown. The cylinders include pistons 38and 40 at the ends of piston rods 42 and 44, the rods being pivotallyconnected to the rear of blade 12. These connections include lugs orbrackets 46 and 48 secured to the blade, and bifurcated portions 50 and52 of rods 42 and 44 are connected to the lugs by means of pins 54 and56 and the rods are shown to be universally connected by the pair ofpins at the rod end on the blade 12.

A pressurized fluid supply is made available for operation of the bladeby means of ahydraulic pump'58 driven from the engine, the pressurizedsystem also includes a reservoir 60, a control valve 62 andinterconnecting lines. The fluid lines are connected to the variouscomponents and in an arrangement such that the lift cylinders arehydraulically parallel. These connections will be further described inmore detail.

In addition to the lift cylinders 30 and 32 for raising and lowering theblade, a tilt cylinder 64 is positioned on the right side of the dozer,as seen in FIGS. 1 and 5. The cylinder is pivotally connected to thepush arm 18 and includes a piston 66 and a rod 68, the rod beingconnected to the blade at one side thereof. by means of a lug or bracket70, a bifurcated portion 72 on the rod and a pin 74. Cylinder 64 isactuated by the pressure fluid to change the position of the blade bytilting one side in relation to the other. FIG. 2 shows the front of thedozer withtlie blade in various angles of tilt. Cylinder 64 responds toa control to change the tilt of the blade wherein one side of the bladeis moved up or down in relation to the other side. The tilt cylinder andits associated fluid lines 63 and 65 and control 67 are shown in FIG. 5.

The hydraulic line connections will now be described as the paralleloperation of the lift cylinders is an important aspect in the practiceof the invention. As seen in FIG. 5, pump 58 is located at the front ofthe engine and an output fluid line 76 is connected to the pump and tothe control valve 62. A line 78 is connected from the valve to thereservoir 60 and a return line 80 connects the reservoir and the pump. Afluid line 82 is connected to the valve and runs forward to a T fitting84 and fluid lines 86 and 88 are connected from the fitting to the rodside of lift cylinders 30 and 32. Lines 90 and 92 are connected to thepiston side of the cylinders and join at a T fitting 94 from which aline 96 runs to the valve. The valve includes an operators handle 98 andis constructed such that actuation of the handle moves the valve spoolfor desired flow of the pressure fluid for raising or lowering of theblade.

In FIG. 3 is shown a sectional view of one of the lift cylindersincorporating the invention, and only one of the cylinders with itscomponents will be described as the construction in each is the same. Asstated, cylinder 30 includes a piston 38 and a rod 42, the rod beinggenerally within the body 100 when the piston is in the retractedposition. Of course, a portion of the rod always extends through one endof the body to connect to the back side of the blade. Body 100 includesa sealing gland 101 at the rod end thereof and the rod moves in thegland under operation of the piston and rod. Adjacent the gland is aport 102 which connects one of the fluid lines mentioned above. Rod 42is secured to piston 38 such that the two move in response to the fluidpressure directed on the piston. A port 105 is positioned at theopposite end 106 of the body 100, and one of the fluid lines isconnected thereto. Piston 38 includes a centrally located bore 108 inwhich is slidably positioned a pair of poppet valves 110 and 112interconnected by a pin assembly 114.

Pin assembly 114 includes an enlarged portion 116 intermediate endportions 118 and 120. Portion 118 is the lower part and is of a lengthequivalent to that of poppet valve 110 and a guide vane 122. Portion 120is the upper part and is longer than portion 118 in that it is enclosedby a guide vane 124 and extends beyond poppet valve 112. Guide vanes 122and 124 have provision for passage of fluid from one end of the cylinderto the other end as the valves are open. Piston 38 includes valve seats126 and 128 at the ends thereof and the bore 108 is sufficiently largerthan the intermediate portion 116 of the pin assembly to provide a fluidpassageway 129 surrounding the pin. The length of the pin assembly 114and the positions at which the poppet valves 110 and 112 are securedthereto are such that only one of the valves can be seated at a giventime. As seen in FIG. 3, portion 120 of the pin extends past the valve112 and is engageable with the upper end 106 of body 100.

Adjacent the piston and on the rod side thereof is an actuating sleeveand pin structure 130. A spring 132, is contained within a portion 134of the sleeve and around the rod 42 and biases the sleeve toward thelower end of the cylinder. Sleeve structure 130 also has a portion 136engageable with gland 101 as the piston is moved to the lower side ofthe cylinder. A pin 138 is contained by portion 136 and positioned to beengageable with poppet valve 110. As seen in FIG. 3, the poppet valveshave enlarged portions 140 and 142 which seat on the piston. FIG. 4shows the piston 38 in a position wherein valve 110 is seated on portion126.

The construction of the hydraulic cylinder and control enables theoperator to tilt the dozer blade at any elevation of the blade withoutfear of twisting the push arms or other parts. This is so because thelift cylinders are directly connected to the blade and the cylinders arehydraulically connected in parallel which allows the pressure fluid toreturn to the supply tank. The poppet valves are aligned within thecylinder and are positioned to permit flow of the fluid in eitherdirection depending upon the fluid pressure and contact with one or theother end of the connecting pin assembly with the cylinder portion.

In the operation of the hydraulic control, pressurized fluid isavailable from the engine driven pump 58 to raise and lower the bladeand to tilt the blade. In the normal raise circuit the fluid flow is tothe rod side of the cylinders as seen in FIG. 5 wherein the piston ismoved upwardly and thus pulls the blade up. The pressurized fluid isdirected through conduits from the control valve and forces poppet valveonto its seat as the piston is moved upward. As the piston approachesthe cylinder end the poppet connecting pin strikes the end of thecylinder and the valves are moved downwardly which unseats valve 110. Asthis valve is unseated the fluid passes by the valve and flows at loadpressure back to the control valve and to the tank.

The action is similar in the normal lowering circuit wherein thepressured fluid is directed on the piston end of the cylinder and therods are extended. Poppet valve 112 is seated on the piston until thepiston approaches the lower end of the cylinder. In this case theactuating sleeve portion 136 strikes the gland and the portion is movedagainst the bias of the spring. Continued lowering of the pistoncompresses the spring by reason of portion 136 against the gland andcontact of poppet valve 110 and the connecting pin portion 118 with theacuating pin 138 moves the poppet assembly upwardly which unseats poppet112 from the piston and permits fluid flow through the piston in thedownward direction.

In certain positions of the lift cylinders, and as the tilt cylinder isoperated, the fluid by-pass pressure are suflicient to hold the load andprevent any twisting of the dozer frame and blade. Since the liftcylinders are in parallel and since the rods are directly connected tothe blade as seen in FIG. 2, this twisting is prevented if one of thecylinders is not at the end of its stroke. The pressure on that cylinderis only that required to hold the blade in position.

Another feature of this construction is the provision for substantialflow in a relatively small diameter cylinder. Also the use of the pistonrod, rather than the piston itself, for enveloping the poppet valveassembly requires only two poppet sealing surfaces to construct andmaintain. The structure requires only one tilt cylinder for tilting theblade either to the right or to the left as the hydraulic lift cylindersare directly connected to the blade and the parallel circuit permitsthem to move freely in response to the pressurized fluid.

It is thus seen that herein shown and described is a relief or releasemeans in the form of poppet valves which valves are aligned with thepiston and are on the same axis with the piston rod, and provide forby-pass of the fluid as the piston approaches one end of the cylinder.While only one embodiment has been shown, variations may occur to thoseskilled in the art, and it is to be understood that all such variationsare contemplated as being within the scope of the invention. Theinvention is not intended to be taken as limited by the embodimentdisclosed, nor in fact, in any manner except as defined in the followingclaims:

What is claimed as new and desired to be secured by letters Patent ofthe United States is:

1. In a vehicle carrying an earth working blade thereon and. having pushbeams pivotally connected to the vehicle and to the blade, hydraulicmeans on said vehicle and including a hydraulic pump and a hydraulicvalve for said pump, a pair of two-way hydraulic lift cylinderspivotally connected to said vehicle and to said blade for raising andlowering said blade and each of said lift cylinders including a piston,a single hydraulic tilt cylinder pivotally connected to said vehicle andto said blade for tilting said blade from side to side, hydraulicconduits connected with said hydraulic means and all said hydrauliccylinders and with said pair of lift cylinders being hydraulicallyconnected together in parallel, a hydraulic passageway extending througheach of said lift cylinder pistons and having spaced-apart valve seats,a poppet valve movably disposed on each end of each of said liftcylinder pistons and each of said poppet valves being movable onto arespective one of said valve seats, for blocking hydraulic flow throughsaid passageway, valve actuating means operatively connected with each'of said poppet valves for moving said poppet valves to open positionson said valve seats, separate abutments included in said lift cylindersfor respectively engaging each of said actuating means upon movement ofsaid piston to each end limit of its stroke and thereby moving therespective one of said poppet valves to its open position and relievinghydraulic pressure in the respective one of said lift cylinders, one ofsaid valve actuating means being a rod connected to one of said poppetvalves, and the other of said valve actuating means including a springfor yieldingly urging the remainder of said other valve actuating meansaway from the other of said poppet valves, whereby said poppet valvesare responsive to hydraulic pressure when said piston is not at eitherof its end-limit positions.

2. The subject matter of claim 1, wherein said remainder of said otherof said valve actuating means includes a sleeve connected with saidpiston and coaxial therewith and movable along the axis of said pistonand being abuttable with said cylinder in response to movement of saidpiston in said cylinder, and said spring axially yieldingly urging saidsleeve away from said piston and toward a position of abutment with saidcylinder, said poppet valves being disposed coaxial with said piston andbeing connected together to be arranged for alternate seating on therespective said valve seats.

References Cited UNITED STATES PATENTS 3,049,820 8/1962 Lichti 172-8032,335,231 11/1943 Armington et al. 37-129 2,543,989 3/1951 Rockwell -522,735,502 2/1956 Muller 91 401 X 3,004,524 10/1961 McCay et al. 91-401 X3,182,563 5/1965 Neilan 91-401 3,184,869 5/ 1965 Olsen 172-803 3,311,0263/1967 Crisp 91-401 FOREIGN PATENTS 26,023 8/ 1910 Great Britain.

ROBERT E. PULFREY, Primary Examiner A. E. KOPECKI, Assistant ExaminerU.S. Cl. X..R.

